French Foreign Minister Jean Francois-Poncet is in the United States this week bearing the message that Western Europe is determined to continue its efforts, begun during the Carter years, to develop a distinct voice of its own in world affairs, however much it seeks close coordination with the Reagan administration.

Francois-Poncet's visit comes when leading French officials perceive a radically new climate in which France's true weight an role in world affairs is taken seriously by the United States for the first time since the presidency of Richard Nixon.

The French foreign minister is scheduled to spend three days in Washington starting Monday seeing the president briefly, Secretary of State Alexander Haig at great length, and Defense Secretary Caspar Weinberger and Treasury Caspar Weinberger and Treasury Secretary Donald Regan. Francois-Poncet then plans to go to Boston to address his alma mater, the Fletcher School of Law and Diplomacy at Tufts University, and to New York to speak at the Council on Foreign Relations.

During the Carter administration, French officials contend, the traditional Franco-American tensions were transformed into "Euro-American" tensions as France and West Germany came to speak with one voice and Britain was gradually pulled into the Franco-German orbit.

Lending one of the first concrete signs of substance to the privately held French offical view that the European trio should serve as an informal "directorate" for the European wing of the Western alliance, the three countries' foreign ministers had an unnanounced meeting in Bonn Feb. 12. It was the first known instance of recent years that the three had gathered just to see each other, rather than consulting in a broader conference.

Moreover, the French obviously consider themselve to be the intellectual and political motor force of the new bloc since Britain is still economically and militarily diminished and West Germany is hobbled by its partition from East Germany and by its heavy dependence on East-West trade.

As respected French elder commentator Raymond Aron wrote a week ago in the news magazine L'Express: "It may be that [Chancellor] Helmut Schmidt share [President Valery] Giscard d'Estaing's ideas on Europe's world role, but he muses above all about Ostpolitik [improving relations with Eastern Europe], which is threatened by the break in the Moscow-Washington dialogue. . . . In tandem with France, he feels stronger to hold the line against the threats from the Kremlin and the pressures from the White House. . . .

"French diplomacy encouraged Ostpolitik. It will not encourage Bonn's slide toward semineutrality. In the French-German couple, France remains the more deeply committed of the two to the Atlantic Alliance."

President Reagan yesterday reinforced the general European perception that he will be tougher with Moscow and a more dependable ally than Carter.Reagan said in an interview with the weekly Figaro magazine that the U.S. commitment to regard an attack on the European allies as an attack on itself is more than a treaty obligation since it is "rooted in our history of close relations and in our current national security interests."

He said that "the American people and the U.S. as a whole would react to the utmost of our capabilities and would fully commit our resources to the defense of Western Europe. Our friends and allies in Europe. Our friends and allies in Europe should understand that this commitment will not diminish while i am presidnet."

He coupled this pledge with reassurances that his adminstration would consult closely with the allies and continue to negotiate with the soviets on strategic nuclear weapons on the basis of mutual concessions that bar the "unhealthy relationship" of giving things away "while receiving nothing in return."

This, French officials indicate, fits with the central theme of French relations with the soviet Union consisting of a combination of both "firmness and dialogue." There is no reason to fret, these officials contend, about differences in tone and rhetoric in what France and the United States say about and to the Soviet Union or even over differences of view on the nature of the East-West struggle.

French officials exultantly say that they are getting high marks from the Reagan foreign policy team for blocking Soviet expansionism in Africa, for the basically unmatched strong French naval cooperation with the Americans around the Persian Gulf, for the strongest budgetary commitment in Western Europe to new defense spending and for stiffeining Bonn's spine against the Soviets.

Under Carter, the French government was stressing its dedication to "dialogue" with the Soviets more than its "firmness." The weak image that Carter projected was a major factor, authoritative diplomatic analysts concluded, in Giscard's vacillating response to the Soviet invasion of Afghanistan: If America was going to act erratically, France could not afford to talk tough to the Soviets.

Another factor that has not gone away, however, is Giscard's need for indirect help from the French Communist Party to roll back Socialist leader Francois Mitterrand's strong bid to unseat him as president in the coming elections.

In a recent television appearance on foreign policy, Giscard spoke softly to the Soviets, and the best thing he had to say about Reagan was that he has a "favorable prejudice" toward him. Many independent observers concluded that he was appealing to Moscow for help in his bid for reelection.

"In the midst of an election campaign, you can't say in this country that you want the United States to be strong and credible, even though that's what he meant to say," observed a friend of Giscard's.

French officials who have gone already to Washington to talk to the new team say that the Reagan aides do not have the same hang-ups the Carter aids did in recognizing that kind of difference between reality and rhetoric.

Still another official with insight into the president's thinking suggested that Giscard is being noncommital toward Reagan because he expects clashes to resume after the current honeymoon.